The present invention relates to a method for producing stacks of folded sheets and, more particularly, for producing a batch of stacks of wet wipes from a limited amount of source material, at a high production speed and in efficiently used floor space.
Wet wipes are typically pre-moistened, disposable towelettes which may be utilized in a variety of applications both domestic and industrial. One particular application is the use of wet wipes for wiping parts of the human body. Wet wipes may also be used for application of substances to the body including removing and applying of make-up, skin conditioners and medications. Another application of wipes is during diaper changes and also for the treatment of adult and baby dermatitis partly caused by the use of diapers and incontinence devices. In addition, wet wipes are also applicable for wiping and/or cleansing other surfaces or for the application of compositions to surfaces, for example, kitchen and bathroom surfaces, eyeglasses, shoes and surfaces which require cleaning in industry, for example, surfaces of machinery or automobiles. Wet wipes can also include articles used for the cleaning or grooming of pets.
Wet wipes are commonly constructed of combinations of synthetic and natural fibers, such as polyolefin fibers, viscose fibers and cotton fibers formed into what is commonly referred to as a web. The webs are generally moistened with an aqueous composition which can contain surfactants, preservatives, oils and scents. The wet wipes are then typically provided in a stack, wherein each of the wet wipes in the stack have been arranged in a folded configuration, such as a z-folded, c-folded, quarter-folded or other configurations. Pop-up wet wipes in which the wet wipes are interfolded with the wet wipes immediately above and below in a stack of wipes are also known to those skilled in the art. The conventional packages are often moisture-proof containers including stacks of discrete wipes, and are typically designed to provide one at a time dispensing which can be accomplished by using a single hand. The containers may have a lid and/or a dispensing aperture.
Automated methods for folding a series of continuous webs into a ribbon of overlapping sheets for use in a pop-up dispensing system, often referred to as interfolding, are known to the art. One method of interfolding is typically performed in a continuous fashion, wherein a multiplicity of webs is provided in a form of multiple parent rolls and wherein each web contributes to one wipe in the stack of wipes. The plurality of webs are normally unwound from the parent rolls by use of unwind stands and dragged through a plurality of folding devices, wherein each folding device is dedicated to folding a particular web. One difficulty with such type of processes is to maintain precise fold dimensions throughout the stack with the large number of individual folding devices, 10 to 80 folding devices, to make accordingly a typical 10 to 80 count stack of individual wipes. Further, such processes employing a large number of folding devices often require relatively high capital investment. Another difficulty with the multiple-web-type processes is to produce a limited size batch of wet wipe products for development purposes without providing a multiplicity of webs, and, thus avoiding the high cost of materials. Still another problem with such processes is that they require a lot of floor space to accommodate the multiplicity of webs and folding devices.
Another method of interfolding utilizes typically two webs which are folded and interfolded by a pair of rotating rolls. A tucker member and vice or suction rolls are typically used to alternatively and transversely fold each piece of web in an intermeshing relation to its immediately preceding piece and its immediately succeeding piece. Although such a method provides more effective use of materials for a limited size batch production, however, these processes are complex and, accordingly, are expensive to manufacture and maintain.
Another problem which particularly relates to the folding of wet webs at high production speeds is the use of conventional folding devices. The conventional folding devices, such as a folding device described in U.S. Pat. No. 4,131,271, often do not work as effectively with wet webs as they do with dry webs at high production speeds. The problems may include wrinkles in the folds and tears of the webs.
Accordingly, it would be desirable to provide a method which is cost effective to produce a limited size batch of wet wipe at high production speed. Further, it would be desirable to provide a method which can be utilized in an efficient floor space. Further, it would be desirable to provide a method which does not require a supply of multiple web materials. Further, it would be desirable to provide a method which does not require use of multiple folding devices. Still further, it would be desirable to provide a folding device that works efficiently with wet web materials at high production speeds.
In accordance with one aspect of the present invention, a method is provided for producing a batch of products having a multiplicity of interfolded, generally rectangular sheets from webs having an advancing velocity in a path of travel of each web. The method includes the steps of folding a first ribbon by feeding a first web in the path of travel of the first web through a first folding device capable of making a longitudinal Z-fold. The Z-fold includes an upper fold portion having an upper width, a middle fold portion underlying the upper fold portion and having a middle width and a lower fold portion underlying the middle fold portion and having a lower width. The method further includes the step of folding a second ribbon by feeding a second web in the path of travel of the second web through a second folding device capable of making a longitudinal Z-fold. The method further includes the step of interfolding the first ribbon with the second ribbon by inserting at least one portion of the first ribbon through an interfolding gap in the second folding device to form a first pair of ribbons, wherein the first ribbon is at least partially overlapped with the second ribbon. The method further includes the step of securing the first pair of ribbons to a perimeter surface of a cyclical accumulator positioned adjacent to the first folding device. Further, the method includes the step of accumulating the first pair of ribbons onto a perimeter surface of the cyclical accumulator by providing a tangential velocity to the first pair of ribbons in a path of travel thereof coinciding with the path of travel of the first ribbon and the path of travel of the second ribbon. The tangential velocity being substantially equal to the advancing velocity of the first web and the second web. Further, the method includes the step of interfolding the first pair of ribbons with a second pair of ribbons by inserting at least one portion of the first pair of ribbons through an interfolding gap in the first folding device. Further, the method includes the step of accumulating the second pair of ribbons onto the perimeter surface of the cyclical accumulator by rotating the perimeter surface of the cyclical accumulator to provide the tangential velocity to a second pair of ribbons, wherein at least one portion of the second pair of ribbons is superimposed onto the first pair of ribbons. Further, the method includes the step of repeating the step of rotating the cyclical accumulator to form successive pairs of ribbons until a desired stack of pairs of ribbons is formed on the perimeter surface of the cyclical accumulator. The method further includes the step of selectively cutting through the stack of pairs of ribbons to provide a batch of products having a multiplicity of interfolded, generally rectangular sheets.